A study of the detection and imaging characteristics of new single gamma emission tomographic system is proposed. The system design is based upon a unique concept - electronic collimation derived from a sequential interaction of the gamma radiation with two position and energy sensitive detectors. This design concept leads to significant gain in sensitivity over conventional gamma cameras. The first detector is thin, and optimized for obtaining Compton interactions. The second detector is thick, and placed behind the first detector to capture as large a fraction of the radiation scattered from the first detector as possible. The proposed research consists of a pilot experiment which will demonstrate the electronic collimation concept, and provide a means to study the various system parameters such as the point spread function, resolution, and sensitivity. In order to do this, a special germanium detector has been fabricated and will be placed in coincidence with a gamma camera (without its collimator). By recording coincidence events between the two detectors, the activity is localized on conical surfaces within the body. A novel iterative algorithm is proposed to reconstruct the three-dimensional activity distribution from these data. This algorithm will be evaluated by extensive computer simulation studies and with actual data obtained from the prototype system.